Seawater Pump Drive Belt – Fits Yanmar 1GM, 2GM, 3GM Series (Replaces 104511-78780, 104511-78780E)
Seawater Pump Drive Belt – Fits Yanmar 1GM, 2GM, 3GM Series (Replaces 104511-78780, 104511-78780E) is backordered and will ship as soon as it is back in stock.
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Delivery and Shipping
Delivery and Shipping
Orders are typically processed within 1–2 business days.
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Seawater Pump Drive Belt – Fits Yanmar 1GM, 2GM, 3GM Series (Replac...
Seawater Pump Drive Belt – Fits Yanmar 1GM, 2GM, 3GM Series (Replaces 104511-78780, 104511-78780E) is backordered and will ship as soon as it is back in stock.
Product Details
This aftermarket Seawater Pump Drive Belt – Fits Yanmar 1GM, 2GM, 3GM Series is an essential component for maintaining your engine's cooling system. It is designed to fit a wide range of Yanmar marine diesel engines, including the 1GM, 2GM, 3GM, 2YM, and 3YM series, covering models produced from the 1980s through the 2000s. Engineered to meet or exceed original equipment standards, this belt ensures reliable performance of your engine-driven water pump.
This part is a direct replacement for Yanmar part numbers 104511-78780, 104511-78780E, and Sierra 97530, providing a precise interchange for a seamless fit.
- Installs as an engine-driven water pump belt.
- Manufactured to OEM specifications for durability.
- The package includes one V-belt for a complete replacement.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number |
|---|---|
| Yanmar | 104511-78780 |
| Yanmar | 104511-78780E |
| Sierra | 97530 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
This belt fits a variety of Yanmar marine engines. Please verify your specific model and check any serial number requirements noted below.
| Brand | Model | Rated HP | Stroke | OEM Part No. | Notes |
|---|---|---|---|---|---|
| Yanmar | 1GMY-C, 1GMY-EC, 1GMYS-C, 1GMYS-EC | 4-Stroke | 104511-78780 | ||
| Yanmar | 2GM, 2GMF | 4-Stroke | 104511-78780 | ||
| Yanmar | 2GM20, N2GM20B, 2GM20C | 4-Stroke | 104511-78780 | ||
| Yanmar | 2GM20F, 2GM20FV, 2GM20FVE, 2GM20V, 2GM20VE | 4-Stroke | 104511-78780 | ||
| Yanmar | 2GM20F-YEU, 2GMFY, 2GMFY-E, 2GMY, 2GMYE-EC | 4-Stroke | 104511-78780 | European manufactured variants | |
| Yanmar | 3GM, 3GMF | 4-Stroke | 104511-78780 | ||
| Yanmar | 3GM30, 3GM30B, 3GM30C | 4-Stroke | 104511-78780 | ||
| Yanmar | 3GM30F, 3GM30FV, 3GM30FVE, 3GM30V, 3GM30VE | 4-Stroke | 104511-78780 | ||
| Yanmar | 3GM30F-YEU, 3GMFY, 3GMFY-E, 3GMFYE-E | 4-Stroke | 104511-78780 | European manufactured variants | |
| Yanmar | 3HM, 3HMF, 3HM35, 3HM35F | 4-Stroke | 104511-78780 | ||
| Yanmar | 2YM15 | 15 | 4-Stroke | 104511-78780 | |
| Yanmar | 3YM20 | 20 | 4-Stroke | 104511-78780 | For Serial #E00304 & after |
| Yanmar | 3YM27A, 3YM30, 3YM30R | 27-30 | 4-Stroke | 104511-78780 | 3YM30: For Serial #E01733 & after |
| Yanmar | YSM8, YSM12 | 8-12 | 4-Stroke | 104511-78780 |
Technical Specs
- Product Type
- Seawater Pump Drive Belt (V-Belt)
- Installation
- Engine-driven water pump belt
- Connection
- Engine pulley system
- Housing Color
- Black
- Dimensions
- Type: V-Belt M Section (M/19)
Width: 9.5 mm (3/8")
Inner Circumference: 482.6 mm (19")
Outer Circumference: 508 mm (20")
Height: approx. 6 mm - Fitting Type
- Engine-specific pulley fit
- Warranty
- 1 Year (varies by seller)
- Other Technical Attributes
- Manufactured to OEM specifications from same materials as originals
What’s in the Box
- 1 x Seawater Pump Drive Belt (104511-78780/104511-78780E)
Installation Notes
- Disconnect the engine's battery for safety.
- Locate the seawater pump and loosen the tensioner pulley or alternator mounting bolts.
- Carefully slide the old, worn belt off the pulleys.
- Inspect all pulleys for wobble, damage, or grease/oil contamination. Clean or replace pulleys if necessary.
- Route the new belt correctly around the pulleys according to your engine's service manual.
- Apply tension to the belt. A common rule is about 1/2 inch (13 mm) of deflection with firm thumb pressure at the longest span.
- Tighten all bolts to secure the tensioner or alternator.
- Reconnect the battery, start the engine, and visually confirm the belt is running smoothly without slipping or squealing.
Troubleshooting & FAQ
How do I confirm this belt fits my specific Yanmar engine?
The most reliable method is to match your existing part number to the ones listed in our Part Number Matrix (104511-78780, 104511-78780E). You can also check your model against our compatibility table. For models like the 3YM20 and 3YM30, be sure to verify your engine's serial number is within the specified range.
What are the signs of a failing pump drive belt?
Common signs include visible cracks, glazing (shiny surface), fraying, or missing chunks on the belt. You might also hear a squealing noise upon startup or see a rise in engine temperature, indicating the water pump is not spinning effectively due to a slipping belt.
How often should this drive belt be replaced?
Preventative replacement is recommended based on your engine manufacturer's service schedule, typically every few hundred hours or every 2-4 years, whichever comes first. Always perform a visual inspection before each season.
My engine model is listed, but has a letter suffix not in the table. Will it fit?
Often, letter suffixes (e.g., 'F' for heat exchanger, 'V' for V-drive) do not change the core engine block or pulley setup for the water pump belt. If the base model (like '3GM30') is listed, it is very likely to fit. However, always double-check by comparing your old part to our pictures and dimensions.
OEM vs. Aftermarket?
This listing is an aftermarket replacement (not OEM). Built to OEM-level specifications with comparable materials. Manufactured in an ISO 9002 facility, batch-inspected for consistency.
Shipping speed & cost
We ship worldwide quickly—typical transit 5–15 days. Standard shipping is free; expedited options appear at checkout where available.
Warranty & returns
Covered by a 1-year warranty against manufacturing defects under normal use. If issues arise, contact support with your order details. Returns are accepted within our standard window (unused & in original condition). See our policy page or reach out for instructions.
Safety & Important Info
- Verify images/specifications vs your original part. If anything differs—even if your model appears compatible—do not purchase.
- This is an aftermarket replacement, not an OEM component.
- Professional installation is recommended for safety and performance.
About Sea Sierra
- Pro-Grade Standards — We supply marine parts engineered to OEM-level tolerances and tested for real-world conditions.
- Fast Global Fulfillment — Free standard delivery to most regions in 5–15 days.
- Manufacturer-Direct Value — Fair pricing without compromising on materials or QC.
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